1. Field of the Invention
The present invention relates to a light emitting diode (LED), and more particularly to an LED that is used as an illuminant of an image sensor.
2. Description of Related Art
The digital image technology has been widely applied for judging and calculating a displacement of a moving object. For an accurate judging and calculating, an illuminant is necessary to the image sensor.
For example, an optical mouse (7) uses the digital image technology to calculate the displacement thereof. The optical mouse (7) comprises a circuit board (71) mounted therein and a complementary metal oxide semiconductor (CMOS) image-sensing module (73) secured on the circuit board (71). A sensing chip (74) is fabricated in the CMOS image-sensing module (73). An LED (8) is mounted on a rear end of the circuit board (71) and a lens (9) mounted on the circuit board (71). The LED (8) is used as an illuminant for the CMOS image-sensing module (73). The lens (9) includes a convex (91) formed near a middle portion of the lens (9) under the circuit board (71), and a prism (92) formed on a rear end of the lend (9) and facing the LED (8).
The sensing chip (74) has an image collecting area via the convex (91) and the light ray from the LED (8) projects on the image collecting area of the sensing chip (74) after a total reflection effect of the prism for providing an illuminant to the sensing chip (74). Consequently, the sensing chip (74) can collecting and transmitting the difference of the sensing surface in a high frequency for calculating the displacement of the optical mouse (7) when the optical mouse (7) is moved.
The lens (9) in mounted under the circuit board (71) and the LED (8) must be arranged to correspond to the prism (92). Consequently, the volume of optical mouse (7) is hard to be reduced and the lens (9) may raise the manufacturing cost of the optical mouse (7).
With reference to FIG. 9, the prism (92) includes a first reflective surface (921) and a second reflective surface (922) for total reflecting the light from the LED (8) to the image collecting area of the sensing chip (74). However, the illumination of light ray is gradually reduced due to an elongated route and the low illumination will cause a bad influence to the accuracy of the sensing chip (74). Consequently, the manufacturer has no choice but to use an LED that has a high illumination to promote the accuracy of the sensing chip (74). However, the high illumination LED usually consumes a high electric power. Consequently, the high illumination LED is unsuitable to a wireless optical mouse that value to power-saving.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional LED that is used as an illuminant of an image sensor.
The main objective of the present invention is to provide an improved LED that is used as an illuminant of an image sensor.
To achieve the objective, the LED in accordance with the present invention comprises a fabricated block, a first electrode and a second electrode contained in the fabricated block for transmitting an electric current to a PN surface of a semiconductor that is contained in the fabricated block and secured in a top portion of the first electrode. The semiconductor has a light-projecting axis forming an acute angle with an elongate line of a bottom of the fabricated block.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.